Hi,
since one week ago i'm observing a very strange behavior that i cannot reproduce but it has happened a once a day up to now.

one of the windows that i am working out of the blue becomes semi-transparent but one cane still work with her and do anything, moving around, resize and even work normally (it has already happened me with a chrome window, a kate window and a qtcreator window as far as i remember).
However if i minimize the window its image stays exactly in the same place only a little more transparent. It does not responds it is like an image we have above the desktop paper (and yes it still remains there if i change the desktop paper) if i then bring again the application it will go to the exactly same place and it is still workable and i can move it and resize it, usually i do that and make it small and a a corner of a screen, because if i close the application the application goes away no trace of its being still active but the image stays at the screen the only way i made it disappearing is to logout.

I really do not know how to report this "bug" as nothing crashes everything remains operational and working properly., but is very weird and for the last week once a day i'm obliged to logout, i have however all the time of the world to close the apps to finish the work i'm doing so not really a huge problem only a nuisance.

my system

opensuse leap 15.3
Plasma 5.22.4
kde frameworks 5.85.0
qt 5.15.2
kernel 5.3.18-59.19
X11
Graphics Mesa DRI intel UHD Graphics 630

well, maybe specifying what "Window" you are talking about could help, is it an application, which one?

Well as just happened again ( really it has happened two or three time after i post this), and in my first post I said it happened to several applications, chrome , kate and qtcreator, so it should be a plasma related issue.

I just made a screenshot for what just happened a qt creator instance became semi transparent i closed it but his phantom remains no way to make him go away other than logout. It is like a background but without any option to change it because if i change the background he still remains there above.

https://drive.google.com/file/d/1-tA4iUxxZ9d1s93_8KOP0n_RopaaLy1M/view?usp=sharing

open a terminal and made a ps -ux | grep creator to show no instance of qt-creator is running.

and then i change the background paper

https://drive.google.com/file/d/1qVe9jtnnsG6IEIJjaHBpHIKXp_iCzVqo/view?usp=sharing

besides this phantom image the computer works without any problem. But well i'm going to logout e login again. As long the frequency is near once a day this is not a real problem.

In both pictures Creator has a PID, so it is very obviously running... try killing that PID

It might be useful to specify your Transparency settings

where do you the the creator pid? I only see the pid from the grep when I search if creator is running.

My bad, seems I didn't have enough coffee...